Composite Ceramic Wavelength Converter and Light Source Having Same

Abstract

There is herein described a composite ceramic wavelength converter having a first phase of an α-SiAlON:Eu phosphor and a second phase of a β-SiAlON:Eu phosphor. The converter may be used in a phosphor-converted light emitting diode to form a light source having a correlated color temperature (CCT) from 2000K to 4500K.

Description

[0001]This application claims the benefit, including claiming the benefit under 35 U.S.C. §§119(e), 120, of the earlier provisional application “Composite Ceramic Wavelength Converter and Light source having same” (internal docket no. 2014P01793US) filed as U.S. Ser. No. 62 / 193,838 filed Jul. 17, 2015.TECHNICAL FIELD[0002]This invention relates to light emitting diodes (LEDs) and in particular to phosphor-converted LEDs (pc-LEDs) wherein the light emitted by the LED is at least partially converted by a phosphor into light having a different peak wavelength.BACKGROUND OF THE INVENTION[0003]Conventional white-light-emitting phosphor-converted LEDs utilize one or more phosphors to partially absorb blue light emissions from InGaN LEDs in order to convert some of the blue light into a yellow light (also referred to as wavelength conversion.) The combination of the remaining unabsorbed blue light and converted yellow light which is finally emitted by the pc-LED is perceived by a human obs...

AI Technical Summary

Benefits of technology

[0009]In accordance with one object of the invention, there is provided a composite ceramic wavelength converter that may be used for warm white pc-LEDs. The composite wavelength converter comprises a combination of rare-earth doped oxynitride and nitride phosphors that have been found to have longer excitation and emission wavelengths compared to oxide phosphors. In particular, the composite ceramic wavelength converter comprises a β-SiAlON:Eu phosphor, an α-SiAlON:Eu phosphor and optionally a CaAlSiN3:Eu phosphor. When the converter is combined with a blue-emitting LED, a warm white pc-LED may be achieved that has a desirable CRI and better thermal and quenching stability.

Problems solved by technology

Unfortunately these red-emitting phosphors are not as efficient, forcing designers to make a compromise between efficient cool white LEDs with low color rendering, or less efficient warm white LEDs with higher color rendering.

In addition, since more than one type of phosphor is needed, warm white LEDs typically use phosphor mixtures dispersed in silicone resins which are susceptible to degradation by UV radiation and temperatures above 200° C. There is also an increased risk of thermal quenching of the emission and larger color shifts over time and temperature.

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